package com.ruiyi.careryun.utils;

import java.io.FileInputStream;
import java.io.IOException;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5Util {
	public static final int BUFFER_SIZE = 4096;
	private static final String MD5_ALGORITHM_NAME = "MD5";

	private static String byteArrayToHexString(byte b[]) {
		StringBuffer resultSb = new StringBuffer();
		for (int i = 0; i < b.length; i++)
			resultSb.append(byteToHexString(b[i]));

		return resultSb.toString();
	}

	private static String byteToHexString(byte b) {
		int n = b;
		if (n < 0)
			n += 256;
		int d1 = n / 16;
		int d2 = n % 16;
		return String.valueOf(HEX_CHARS[d1] + HEX_CHARS[d2]);
	}

	public static String MD5Encode(String origin, String charsetname) {
		String resultString = null;
		try {
			resultString = new String(origin);
			MessageDigest md = MessageDigest.getInstance("MD5");
			if (charsetname == null || "".equals(charsetname))
				resultString = byteArrayToHexString(md.digest(resultString.getBytes()));
			else
				resultString = byteArrayToHexString(md.digest(resultString.getBytes(charsetname)));
		} catch (Exception exception) {
		}
		return resultString;
	}

	public static String fileMD5(String inputFile) throws IOException {

		FileInputStream fileInputStream = null;
		DigestInputStream digestInputStream = null;

		try {
			// 拿到一个MD5转换器（同样，这里可以换成SHA1）
			MessageDigest messageDigest = MessageDigest.getInstance(MD5_ALGORITHM_NAME);

			// 使用DigestInputStream
			fileInputStream = new FileInputStream(inputFile);
			digestInputStream = new DigestInputStream(fileInputStream, messageDigest);

			// read的过程中进行MD5处理，直到读完文件
			final byte[] buffer = new byte[BUFFER_SIZE];
			while (digestInputStream.read(buffer) > 0)
				;
			// 获取最终的MessageDigest
			messageDigest = digestInputStream.getMessageDigest();
			// 拿到结果，也是字节数组，包含16个元素
			byte[] digest = messageDigest.digest();
			// 同样，把字节数组转换成字符串
			return new String(encodeHex(digest));

		} catch (NoSuchAlgorithmException e) {
			return null;
		} finally {
			try {
				digestInputStream.close();
			} catch (Exception e) {
			} finally {
				try {
					fileInputStream.close();
				} catch (Exception e) {
				}
			}

		}

	}

	public static char[] encodeHex(byte[] bytes) {

		/*
		 * //
		 * new一个字符数组，这个就是用来组成结果字符串的（解释一下：一个byte是八位二进制，也就是2位十六进制字符（2的8次方等于16的2次方）
		 * ） char[] resultCharArray = new char[bytes.length * 2]; //
		 * 遍历字节数组，通过位运算（位运算效率高），转换成字符放到字符数组中去 int index = 0; for (byte b :
		 * bytes) { resultCharArray[index++] = HEX_CHARS[b >>> 4 & 0xf];
		 * resultCharArray[index++] = HEX_CHARS[b & 0xf];
		 * 
		 * }
		 */

		char chars[] = new char[32];
		for (int i = 0; i < chars.length; i = i + 2) {
			byte b = bytes[i / 2];
			chars[i] = HEX_CHARS[(b >>> 0x4) & 0xf];
			chars[i + 1] = HEX_CHARS[b & 0xf];
		}
		// 字符数组组合成字符串返回
		return chars;
	}

	private static final char[] HEX_CHARS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E',
			'F' };

}
